The Status of Bird Species - Back From The Brink—success Stories

The Peregrine Falcon

Many falcon species have declined with the spread of humans. Like other predatory species, falcons were often hunted, either for sport or because they were considered a threat to chickens or livestock.

The peregrine falcon is the fastest bird on Earth. It can achieve diving speeds of over 200 miles per hour. Like the bald eagle, much of the species' decline was due to the pesticide DDT. Populations sank to approximately 325 nesting pairs during the 1930s and 1940s. The recovery of this species was made possible by the banning of DDT as well as the establishment of special captive breeding centers on several continents. Between 1974 and 1999 more than 6,000 peregrine falcons were released into the wild. Federal and state agencies contributed to the conservation effort, as did private organizations such as the Peregrine Fund, Santa Cruz Predatory Bird Research Group, and Midwestern Peregrine Falcon Restoration Project.

In 1996 the Fish and Wildlife Service declared the peregrine falcon "officially recovered" and began the process to remove the species from the Endangered Species List. The American peregrine falcon was delisted in 1999 across its entire range, although it will be monitored for the next five years to assure that its recovery continues. By August 1999 about 1,650 breeding pairs of peregrine falcons inhabited the lower forty-eight states and Canada, with additional populations surviving in Mexico. The Arctic peregrine falcon, which recovered on its own after DDT was made illegal, was delisted in 1994. However, as of 2002 the Eurasian peregrine falcon, which occurs in Eurasia south to Africa and the Middle East, is still listed as endangered across its entire range.

The Bald Eagle

Almost everyone recognizes the bald eagle (see Figure 8.5). Symbol of honor, courage, nobility, and independence (eagles do not fly in flocks), the bald eagle is found only in North America, and its image is engraved on the official seal of the United States of America. There were an estimated 100,000 bald eagles in the Unites States in the late eighteenth century when the nation was founded.

The bald eagle nests over most of the United States and Canada, building its aerie, or nest, in mature conifer forests or on top of rocks or cliffs. Its nest is of such a grand size—sometimes as large as a small car—that a huge rock or tree is necessary to secure it. The birds use the same nest year after year, adding to it each nesting season. It is believed that eagles mate for life. Bald eagles prey primarily on fish, water birds, and turtles.

Bald eagles came dangerously close to extinction in the twentieth century, largely due to the pesticide DDT, which was introduced in 1947. Like other carnivorous species, bald eagles ingested large amounts of DDT from poisoned prey. DDT either prevents birds from laying eggs or causes the eggshells to be so thin they are unable to protect eggs until they hatch. The Bald Eagle Protection Act of 1940, which made it a federal offense to kill bald eagles, helped protect the species. However, numbers continued to dwindle and the bald eagle was listed as endangered in 1967.

Bald eagle populations started to recover with the banning of DDT in 1972. The species also benefited from habitat protection and attempts to clean up water pollution. In 1995 the bald eagle was moved from endangered to threatened status FIGURE 8.5
The bald eagle was once endangered due to habitat destruction and pollution by pesticides such as DDT. Its populations have recovered with protection and a ban on DDT. (Field Mark Publications) on the Endangered Species List. In 2000, surveys showed that there were about 5,800 breeding pairs in the forty-eight contiguous states. The species was proposed for delisting in 1999; that proposal was still awaiting action in 2004.

Aleutian Canada Goose

The Aleutian Canada goose was first placed on the Endangered Species List in 1966, when there were an estimated 800 individuals. The species had been thought extinct for several decades until a remnant population was discovered in 1962 by Fish and Wildlife biologists on a remote Aleutian island. Deterioration of habitat and the introduction of predators such as Arctic foxes and red foxes were blamed for the animal's decline. The goose population rebounded to 6,300 in 1991, and there were well over 35,000 geese by 2002. Conservation efforts included captive breeding, removal of foxes, and relocation and reintroduction of geese to unoccupied islands. The Aleutian Canada goose was officially delisted by the Fish and Wildlife Service in 2001. A graph of population growth over time for this recovered species is shown in Figure 8.6. Table 8.4 shows some of the important events contributing to the recovery of this species.

FIGURE 8.6
Peak counts of Aleutian Canada geese on wintering areas in California, 1975–2000

TABLE 8.4
Decline and recovery of the Aleutian Canada goose population